Electric organ



April 22, 1952 w.` HAKKARINEN ELECTRIC ORGAN 5 Sheets-Sheet l Filed pee.17, 194? |80. Ha ,20a ZIO. 22o.

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lll /l April 22, 1952 W, HAKKARINEN 2,593,442 Y ELECTRIC ORGAN FiledDeo. 17, 1947 3 Sheets-Sheet 2 -TGZ. 15

April 2,2,k 1952 w. HAKKARINEN ELECTRIC ORGAN m s JWE m @0. NN N ON Q o.f s) H hw m. ml, SM @uw L@ Filed Dec. 17, l'?

Patented Apr. 22, 1952 UNITED STATES. PATENT crFlcE 2,593,442 ELECTRICoRGAN William Hakkarinen, Washington, D. C. applicati@ December 17,1947', serial No. 792,164

(ci. s4"-1.26

10 Claims. 1

My invention relates particularly to electronic I systems and moreparticularly to a circuit arrangement for electric organs.

One of the objects of my invention is to provide a circuit arrangementfor an electric organ of great simplicity which may be inexpensivelymanufactured.

- Another object of my invention is to provide an electric circuitarrangement in which the control keyboard may be operated at a safepotential above earth and may be uninsulated and not constitute a hazardto the operator with respect to possible electric shock during operationof the organ.

Another object of my invention is to provide an improved circuitarrangement for generating a wide range of audible frequencies over themusical scale employing a minimum of electric equipment.

A further object of my invention is to provide a circuit arrangement forgenerating musical notes including an electric circuit in which thedynamic plate-cathode resistance is a function of the cathode-platecurrent for producing different oscillation frequencies.

A still further object of my invention is to provide an electron tubecircuit arrangement for electric organs in which power' losses may beintroduced into the pate circuit in proportion to changes in dynamicresistance for developing, across a load impedance in the electron tubecircuit, conditions which cause the generation of oscillations atdifferent frequencies.

A. still further object of my invention is to provide an arrangement ofkeyboard operated electric organ oscillation circuits controllable overa musical frequency range which may be readily associated with the radioand audio frequency portion of a conventional radio broadcast receiverfor utilizing the sound reproducing system of a radio receiver as areproducer of musical notes under control of the electric organ coveredby my invention.

A still further object of my invention is to provide an improvedconstruction of keyboard for electric organ circuits comprising ametallic stamping having intricately related fingerccntrolledresiliently displaceable key members.

Other and further objects of my invention reside in the improved circuitarrangement for electric organs and keyboard control therefor as setforth more fully in the specification hereafter following, by referenceto the drawings,

in which:

. Figure 1 schematically illustrates the keyboard Vcontrolled oscillatorsystem of my invention for ofconnection thereof to an audio frequencyamplifying and sound reproducing system or to a head set forreproduction of the musical notes;

Fig. 3 is a transverse sectional View taken substantially on line 3 3 ofFig. 2 and illustrating on an enlarged scale the construction of thekeyboard employed with the organ circuit of my invention; and y Fig. 4schematically illustrates an adaptation of the electric organ circuit ofFig. l in which the output signal isA impressed between the grid andcathode of an electron tube which is generating radio frequencyoscillations. Thus the radio frequency signal is modulated by the signalfrom the organ and acts as a carrier for the organ signal so that theorgan can be played over a nearby radio receiver with no connectionbetween the two required.

My invention is directed to an electric organ circuit which is verysimple to manufacture and which may be produced on a mass productionscale at low cost.

The circuit arrangement of my invention eliminates the complicatedarrangemement of relaxation oscillators and the utilization of variousresistor-condenser and inductance-condenser circuit components and thecomplications of tone frequency generators of the electrostatic andelectromagnetic type receiver required in generating tones in electricorgans. My invention erated are controlled by operating a transformervfeed-back vacuum tube oscillator at a very low plate voltage and 'smallplate current, under which conditions the frequency at whichoscillations can be sustained varies with the amount of plate currentflowing through the electron -tube.

With fixed capacitor, inductor and resistor values in the oscillatorcircuit one need only to change the cathode-plate current to cause achange in frequency. It is only necessary,

then, to aect the electron tube with means `which vary the cathode-platecurrent, or, what is effectively the "equivalent,- 'the dynamic platere- 3 sistance of the electron tube to control the generated frequency.

The electric organ of my invention has been developed particularly foruse as an attachment to conventional radio broadcast receivers forreadily converting the conventional broadcast receiver into anelectricorgan.

The output of the electric organ circuit of my invention is applied tothe radio frequency input or to the audio frequency amplifier and soundreproducing system of the conventional radio broadcast receiver, forreproducing, through the loud speaker of the radio broadcast receiver,the range of musical notes controlled by the'electric organ keyboard. Itis realized that the electric organ of my invention may be produced as acomplete instrument, vin itself. embodying an audio frequency amplifierand sound reproducing system. However, from the description hereinafterfollowing it will be understood that the electric organ assembly may bea compact unit readily adaptable as an yauxiliary device to conventionalradio broadcast receivers already available in the home forfobtainingmuch added enjoyment from a conventional radio receiver.

Referring to the drawings in detail, reference character Idesignates-1a' combined rectifier and oscillator tube which, 'for thepurposes of explaining my invention,.may be designated as the 117N'1type. The tube includes heater 2 cathode 3 for the oscillator, controlgrid 4 for the oscillator, screen grid 5 and plate 6. The rectierportion of the tube includes the rectier cathode i and the rectifier ordiode plate 8. The tube circuit is connected to an alternating currentsystem forming a supply line without the interposition of a powertransformer to isolate the power line from the direct current voltagesrequired- The power line. connection for the circuit is reuresentedat. 9extending through control switch I0 to the heater 2. The direct currentvoltage required in the tone generating circuits isl secured byrectifying the alternating current from the power supply circuit 9 inthe diode portion of the tube I. y power line from thel direct currentvoltages required is accomplished by the circuit arrangement includingresistors II and l2 and I4. connected between the rectifier cathode 1and one side of the power supply 9 at 9d. Because of the small power andvoltage requirements 0f the toneeenerator these resistanees may besumciently large to limit the alternating current which can ow betweenthe. oscillator ground and either side of the power line 9 to a Valuewhich is non-dangerous to an operator touching the metallic keyboardwhich is used. in. the system of my invention.l

A non-insulated keyboard is employed with the oscillator system or myinvention SQ it makes no difference whether the operator contacts thekeyboard,Y er not This results from the circuit arrangement by which theoscillator ground is The isolation of the pleted through the oscillatorground and through resistor I2 to tap 26. rihe inductive winding 23 ismagnetically coupled with inductive winding 24 through magnetic core 25.Magnetic winding 24 connects between plate electrode 8 and the tap 26between resistors II and i2 in the resistive circuit leading to thepower supply line 9 in the path included in the rectifier portion oftube I. Thus, a regenerative coupling is provided between the controlgrid circuit of tube I and the plate circuit of tube I for thegeneration of oscillations therein. A by-pass condenser 21 connectsbetween the ends of inductive windings 23 .and 24 immediately adjacentthe control grid #l c ondensers disposed in a shunt path with theconnected to either side of the line supply voltage 9 through resistorsIl and I4 respectively. The

frequency generated is varied by limiting the cathode to plate current,that is, the current ow from cathode 3 to plate 5 by the self-biasingaction of the amount of resistance from resistor I5 which is included inthev circuit between cathode 3, adjustable resistor I8 includingadjustable tap I1, and connections through any one of the keysrepresented at I8, I9, 20, 2I and 22 connected through adjustable taps18o, 19u,r 20a, 21a and 22a. on resistor I5, the circuit beingcomresistors as shown, that is, condenser` 2B is connected in shunt withthe series arranged resistors II, I2 and I4 and condenser 29 isconnected in shunt with resistor i2. Condenser 28 floats above eitherside of line potential so that resistors II and Ill can effectivelyisolate tap 26 or oscillator ground from the line shown at 9. The outputof the oscillator system is coupled through condenser 3B with theresistive circuit constituted by resistance 3| across which the outputterminals 32 connect through the resistance 3B.

The keyboard construction employed for the control of the electric organcircuit is illustrated in Figs. 2 and 3. The oscillator system isassembled, as represented at 34 in Fig. 2, on a base support 35 whichalso provides mounting means for the sub-base 36 which carries theresistor, represented at I5, corresponding to the resistor I5 in Fig. 1.The resistor l5 is generally of the wire-wound type extending verticallyto enable adjustable tap connections to be made with the resistancewinding by the several taps which I have represented at Ia, ida, 2cd,2m, and 22a extending from terminal points ESD, I9b, 2Gb, 2lb and 22b,etc., leading to the keys designated in Fig. 1 as I8, I9, 20, 2| and 22respectively. A symmetrically arranged set of taps is provided adjacentthe opposite side of base 36 leading to other keys of the keyboardsystem. rhe key- .board system is representedas comprising a pair offlat resilient metallic plates designated by reference characters 31 and3.3. The metallic plates 31 and 38 are spacially related to each otherby means of the supporting sub-base 39 and the supporting members 48 and4I carried thereby. Supporting member 48 provides a support for theresilient plate S8. Resilient plate 33 is divided into a multiplicity oftransversely extending tongues which form keys and which may beindividually depressed to establish electrical connection with contactmembers supported beneath the ends of the keys, as represented, forexample, in Fig. 3. Similarly, resilient plate 31 is supported onsupporting member lli and the individual keys thereof may be depressedto establsh connection with the contacts positioned beneath the plate asrepresented at 43. The contacts 43 are arranged at spaced intervalsalong the strip of insulation material 6,5 mounted on supporting member66 as shown. Each of the plates 31 and 38 are slotted, as represented at31a and 38a to provide, in effect, a combined structure in which thelaterally extending flexible resilient strips constitute keys of theorgan and may be depressed to establishconnection with the contactslocated below the ends of the strips. Re.- siliency or flexibility isimparted to the several keys by reason ofthe punched out or slottedconstruction represented at 37a and 38a which may be further augmentedby the recessed construction represented for example at 31o and 31e. Inorder to simulate a piano or organ keyboard I may omit certain of thekeys in the positions 31d, 31e, etc. Also, I further simulate aconventional keyboard by painting the keys 31 black and keys 33 white.Thus, different values of resistance on the tap resistors I5 may beintroduced into the cathode plate circuit. The output of the oscillatorsystem at 32 may be connected through lead 45, represented in Fig. 2, toa plug connector 44, which may be inserted into the audio frequencyinput of the conventional radio brcadcast receiver so that the amplifierand sound reproducing system of the conventional radio broadcastreceiver operates to reproduce the musical notes secured by changes inthe cathode resistor l5. In the arrangement shown I have successfullycovered the range of musical notes Ge through Fe but I desire that it beunderstood that various ranges may be readily covered. Where it isdesired to reproduce merely the musical notes developed by theoscillator system, without amplication through the broadcast receiver,the output circuit 32 is connected to the head telephone receivers 45,as represented in Fig. 2. The power line cord is di' and the maleconnector 46.

The cathode plate current ow is interrupted by the keyboard action toprevent any time delay from the closing of a keyboard switch and thegeneration of a frequency such as would occur if the keyboard switchonly acted in the grid to cathode circuit.

The ampliner circuit is made to feed back to its own input circuit avoltage of the proper phase and amplitude for generating oscillations.The necessary conditions are that the voltage fed back from the outputcircuit is about 180 degrees out of phase with voltage developed acrossthe load impedance in the plate circuit and that the feed-back voltageshave sufficient magnitude to develop the output power necessaryto-produce the input voltage. In this circuit the phase differencerequired is mostly developed by the feed-back transformer when properlyconnected. The frequency at which the oscillations occur in this lowpower oscillator circuit, in which resonant circuits are not used, isthe frequency at which the feed-back voltage is of exactly the properphase and amplitude to permit the electron tube to supply the requisiteinput voltage. Therefore, when the plate current is limited to certainvarious values, the power' output developed across the load impedance isvaried and as the frequency at which oscillations can occur is afunction of the power developed across the load impedance which, inturn, is governed by the cathode to plate current within the tube, thefrequency is controlled by the amount of plate current flowing.

Viewed from another angle, the dynamic platecathode resistance is infunction of the cathode- Thus, the power lossesplate current flowing.introduced into the plate circuit vary with the changes in the dynamicresistance, and, as a result of these losses, the power developed acrossthe load impedance varies, which is a condition to permit the oscillatorto supply different frequencies. The adjustable multi-tapped resistor I5is used either as a voltage divider or the equivalent of a bank ofvariable resistors. With this arrangement the organ can be tuned toexactly the desired frequencies even though the elec- 'iv tricalcharacteristics of the vacuum tube l and the transformer 23-25-24 mayvary widely.

Referring to Fig. 4 in detail, reference number 49 designates a combinedrectifier and amplifier tube similar to electron discharge tube I inFig. l, except for the heater 5i] which is supplied with a differentvoltage. Another` electron discharge tube 5i with heater 52 in seriesconnection with heater 5G, has a cathode 53, control grid 5d, screengrid :'55, and plate 55, and is used to generate a radio frequencysignal in conjunction with inductor winding 51 which is regenerativelycoupled to inductor 58. Condenser !59 resonates inductor 53 and thetuned circuit is coupled to the control grid 54 by condenser G. Theaudio frequency signal is coupled through condenser to resistor S2 whichconnects to cathode 53 and to resistor 6| joined to the grid 58.Resistor 63 connects tap 26 to inductor 5'! and plate oy-pass condenser611 which joins to cathode The oscillator system connected with tube 5iis designed to produce radiation over a suilicient distance to couplewith the circuits of the standard broadcast receiver arranged in theneld of the oscillator so that no physical connection between the organunit and the broadcast receiver is required. Moreover, the constants ofthe circuit of the oscillator of tube 5I are designed so that modulationmay be produced over the Ientire frequency spectrum determined by theAcuit connected with oscillator tube El.

rPhe system of my invention has been found to be very practical inoperation and considerably adds to the enjoyment of the use of theconventional radio broadcast receiver when operated from time to timea-s an electric organ.

I realize that modications may be made in the circuit arrangement andthe manner of applying the generated frequencies to the soundreproducing system, and I desire it to be understood that no limitationsupon my invention are intended other than may be imposed by the scope ofthe appended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is as follows:

l. A system for producing electrical oscillations comprising an electrontube including at least a cathode, a control grid, and an anode, aninput circuit interconnecting said cathode and control grid, an outputcircuit interconnecting said anode and cathode, means regenerativelycoupling said circuits for the production of oscillations, a resistanceconnected in common to said input and' output circuits, a multiplicityof progressively arranged taps on said resistance terminating incontacts, keys depressible to contacting relation with said contacts andconnected in a path common to said input and output circuits foreffecting step by step loading of both said input and output circuitsand an additional resistance connected in said input circuit andselectively adjustable for variably loading said input circuit.

2. A system for producing electrical oscillations comprising an electrontube including a cath- 6de, a control grid, and an anode, an inputcircuit interconnecting said cathode and control grid, an output circuitinterconnecting said anode and cathode, means regeneratively couplingsaid circuits for the production of oscillations, a resistance device, aplurality of progressively arranged taps on said resistance device, amultiplicity or" depressible keys having coacting contacts alignedtherewith, a connection extending from said cathode to said keys,connections extending from said coacting contacts to said taps, and anadditional resistance device connected in circuit with said inputcircuit and selectively adjustable for variably loading said inputcircuit.

3. A system for producing electrical oscillations comprising an electrontube including a cathode, a control grid, and an anode, an input circuitinterconnecting said cathode and control grid, an output circuitinterconnecting said anode and cathode, means regeneratively couplingsaid circuits for the production or" oscillations, a resistance deviceconnected in a path common to said input and output circuits, amultiplicity of progressively arranged taps on said resistance device,contacts connected to each of said taps, selectively depressible keyscoacting with each of said contacts for introducing into said circuitspredetermined increments of power losses for correspondingly changingthe frequency of oscillation of said circuits, and an additionalresistance device connected in circuit with said input circuit andselectively adjustable for variably loading said input circuit.

4. A system for producing electrical oscillations comprising an electrontube including a cathode, a control grid, and an anode, an input circuitinterconnecting said cathode and control grid, an output circuitinterconnecting said anode and cathode, means regeneratively couplingsaid circuits for the production of oscillations, means for selectivelyproducing increment by increment changes in the dynamic plate-cathoderesistance of said circuits for producing corresponding changes inthecathode-anode current now in said circuits, and separate means connectedin circuit with said input circuit and selectively adjustable forvariably loading said input circuit.

5. A system for producing electrical oscillations comprising an electrontube including a cathode, a control grid, and an anode, a separatecathode and anode, an input circuit interconnecting said rst mentionedcathode and said control grid, an output circuit interconnecting saidrst mentioned cathode and anode, means regeneratively coupling saidcircuits for the production of oscillations, a source of alternatingcurrent, a heater for each of said cathodes energized from said sourceof alternating current, circuit connections for said second mentionedseparate cathode and anode for rectifying said alternating current andapplying the rectified current to said circuits, a resistive loadhaving, a series oi progressively arranged taps thereon, contactsconnected with said taps, keys selectively depressible into contactingrelation with said contacts, a circuit eX- tending through saidresistive lead and through said keys in a path common to said input andoutput circuits, and a separate resistive load connected in circuit withsaid input circuit and selectively adjustable for variably lcadingsaidinput circuit.

6, A system for producing electrical oscillations comprising an electrontube including a cathode, a control grid, and an anode, a separate`cathode and anode, an inputV circuit interconnecting said firstmentioned cathode and said control grid, an output circuitinterconnecting said rst mentioned cathode and anode, meansregeneratively coupling said circuits for the production ofoscillations, a source of alternating current, a heater for each of saidcathodes energized from said source of alternating current and applyingthe rectified current to said circuits, an impedance load having aseries of progressively arranged taps thereon, contacts connected withsaid taps, keys selectively depressible into contacting relation withsaid contacts, a circuit eX- tending through said impedance load andthrough said keys in a path common to said input and output circuits,and a separate impedance load connected in circuit with said inputcircuit and selectively adjustable for variably loading said inputcircuit.

7 A system for producing electrical oscillations comprising an electrontube including a cathode, a control grid, and an anode, an input circuitinterconnecting said cathode and control grid, an output circuitinterconnecting said anode and cathode, means regeneratively couplingsaid circuits for the production of oscillations, means for producingstep by step changes in the dynamic anode-cathode eiective resistancefor producing corresponding changes in cathode-anode current flow, acoacting electron tube circuit comprising anoscillator, a resistorelement having a multiplicity of spaced progressively arranged tapsthereon, a multiplicity of selectively controllable playing keysindividual to said taps, said resistor element and said keys beingconnected in circuit between the control grid and cathode of said rstmentioned tube, and means controlled by changes in current flow in saidfirst mentioned circuits for determining the frequency of operation ofsaid oscillator over the range of frequencies resulting from changes inthe dynamic anode-cathode resistance of said first mentioned circuits.

8. A system for producing musical tones, an electron tube including acathode, a control grid, an anode, an input circuit interconnecting saidcathode and control grid, an output circuit interconnecting said anodeand cathode, means regeneratively coupling said circuits for theproduction of oscillations, a resistive device connected in common withboth said input and output circuits, a multiplicity of progressivelyarranged to each of said taps, separate resistive means for Vvariablyloading said input circuit, and selectively depressible keys coactingwith each of said contacts for supplying said input and output circuitswith predetermined increments or" direct current power, said incrementsof direct current power producing corresponding increments ofalternating current power in the output circuit, and said increments ofalternating current power in said output circuit controllingthefrequency of oscillation of said circuits.

9. A system for producing musical tones, an electron tube including acathode, a control grid, an anode, an input circuit interconnecting saidcathode and control grid, an output circuit interconnecting said anodeand cathode, an audio frequency transformer system including a pair ofelectromagnetically coupled windings with one of said windings in saidinput circuit and the other of said windings in said output circuit forregeneratively coupling said circuits for the production of audiofrequency oscillations, a resistance device common to said input andoutput circuits, a multiplicity of progressively arranged taps on saidresistive device, contacts connected to each of` said taps, a separateadjustable resistance device individual to said input circuit,selectively depressible keys coacting with each of said contacts forsupplying said input and output circuits with predetermined incrementsof direct current power, said increments of direct current powerproducing corresponding increments of alternating current power in theoutput circuit, said increments of alternating current power in saidoutput circuit controlling the frequency of oscillation generated bysaid circuits.

10. An oscillator for developing non-linear voltage waves of complexform comprising a thermionic tube including at least a cathode, acontrol electrode and an anode, a circcuit path connected between saidcontrol electrode and said cathode, said path including an adjustableresistor, a multiplicity of keys, a multiplicity of contacts coactingwith said keys, a resistor element in said circuit path havingprogressively arranged spaced taps thereon, connections between saidtaps and said contacts, the end of said resistor element which connectswith said circuit path being connected to a point of predeterminedpotential, a transformer winding included in said circuit path andconnected to said point of predetermined potential and to said controlelectrode of said thermionic tube, a capacitor directly connectedbetween said control electrode 3u and said anode of said thermionictube, a trans- 10 former winding coupled in feedback relation to saidrst mentioned transformer winding and connected intermediate the saidanode and a point of positive potential, output terminal means, acircuit including a pair of resistors, a condenser connected to saidanode and to a common connection to said pair of resistors, the rst ofsaid resistors being connected` between said last named condenser andsaid point of predetermined potential, and the second of said pair ofresistors being connected in series with said output terminal means andsaid point of predetermined potential.

WILLIAM H AKKARINEN.

REFERENCES CTED The following references are of record in the le of thispatent:

UNITED STATES PATENTS Number Name Date 497,144 Teal May 9, 18931,033,786 Cox July 30, 1912 1,180,720 Howe Apr. 25, 1916 1,539,402Nichols May 25, 1925 1,771,905 Uher, Jr July 29, 1930 1,823,724 CarlsonSept. l5, 1931 2,211,540 George Aug. 13, 1940 2,301,871 Hanert Nov. l0,1942 2,328,282 Kock Aug. 3l, 1943 2,396,439 Schlesinger Mar. 12, 1946

